1. Field of the Invention
The present invention relates to a heating resistor which is high in specific resistance and superior in stability in heat-resist property and relates to a thermal head using the same.
2. Description of the Prior Art
Generally, a thermal head is arranged in such a manner that a heating resistor layer for forming dot-like heating resistors, a power supply conductive layer for supplying the heating resistor layer with a current, and a protecting layer for protecting those layers from oxidation and abrasion are laminated one on one on an electrically insulating substrate made of ceramic, or the like, with its surface convered with a thin glass-glazed layer.
Conventionally, a thin film of tantalum nitride (Ta.sub.2 N) is widely used as the foregoing heating resistor layer. The tantalum nitride thin film is superior in stability and reliability as a heating resistor.
However, since the specific resistance of the tantalum nitride thin film is about 240 .mu..OMEGA.-cm, the thickness of the film is required to be made extremely thin so that the lifetime property thereof is too poor to use in the case where high sheet resistivity such as 50 .OMEGA./.quadrature. or more is required. A thermal head using a tantalum nitride thin film as a heat resistor layer has such a characteristic that the resistance value decreases when the surface temperature of the heating portion becomes 400.degree. C. or more, and if the temperature further rises to 500.degree. C. or more, the amount reduction in resistance value reaches 10% or more of the initial value. This is the reduction in resistance value due to progressing of recrystallization of tantalum nitride at a high temperature, resulting in one of serious problems in the case of using tantalum nitride at a high temperature.